Fig. 1. Structural model and possible H adsorption sites of single-layer MX₂. Blue, orange and pink balls correspond to anions (X²⁻), cations (M⁴⁺) and hydrogen atoms, respectively. A−F shows a possible adsorption site for hydrogen atom. 单层MX₂的结构模型及可能的H吸附位点示意图, 其中蓝色, 橙色和粉色分别表示阴离子(X²⁻)、阳离子(M⁴⁺)和氢原子; A—F表示氢原子可能的吸附位点

Fig. 2. Binding energy of the stable adsorption sites of single-layer MX₂. 单层MX₂的稳定吸附位点结合能统计图

Fig. 3. Diffusion barrier of hydrogen atoms through a single layer of MX₂. The diffusion path is from the D point of surface through the interlayer E point to the other surface D' point. 氢原子穿过单层MX₂的扩散势垒(扩散路径为从单层MX₂表面D点穿过层间E点扩散到另一个表面D'点)

Fig. 4. Charge transfer profile of hydrogen atoms adsorbed on a single-layer MX₂. The calculated charge transfer is the transfer of the E site of the MX₂ layer, and the arrows indicate the direction of charge transfer. 氢原子稳定吸附在单层 MX₂的电荷转移分布图(计算的电荷转移为MX₂层E位点的转移情况, 箭头指示电荷转移的方向)

Fig. 5. Band structures of 4 × 4 monolayer MX₂ (1L-MX₂) supercell. The fermi level is represented by dotted black line and set as 0 eV. 4 × 4单层MX₂ (1L-MX₂)超胞的能带结构图(费米能级用黑色虚线表述并设为0 eV)

Fig. 6. Band structures of surface hydrogenation MX₂. Blue and red correspond to spin-up and spin-down, respectively. 表面氢化MX₂能带结构图(蓝色和红色线分别表示自旋向上和自旋向下)

Fig. 7. Band structures of interlayer hydrogenation MX₂. Blue and red correspond to spin-up and spin-down, respectively. 层间氢化MX₂能带结构图(蓝色和红色线表示自旋向上和自旋向下)

Table 1. Binding energy of possible adsorption sites (AS) of hydrogen atoms adsorbed on single-layer MX₂, and M—H (M⁴⁺ = Mo, W) bond lengths.